What’s a big Catholic church doing on İstiklal Caddesi in the middle of Istanbul?
Plenty! France, Italy and other predominantly Catholic countries had significant commercial and diplomatic relations with the Ottoman Empire. The Church of St Anthony of Padua (usually called St Antoine here) was established here in 1725 to serve transient foreigners and the many families who stayed on in the sultan’s dominions.
The present red brick Italian neo-Gothic building replaced the older church in 1913.
You probably won’t see any priests or nuns on the street–at least, you won’t see them in their religious garb. When Turkey became a secular state with the proclamation of the Turkish Republic in 1923, clergy and other religious persons of all faiths were forbidden to wear religious raiment in public places.
Turbans, mitres, pastoral collars and nuns’ habits are restricted to the interiors of religious buildings, private homes and vehicles.